1. Field of the Invention
The invention generally relates to a system including remotely related thermocouples employed in detecting and measuring temperatures by providing electrical output signals to be compared with the electrical output signals derived from reference thermocouples maintained at known temperatures, and more particularly to an improved oven for maintaining the junctions of a plurality of reference thermocouples at a common and constant temperature.
2. Description of the Prior Art
As is well known by those familiar with temperature measuring procedures commonly employed in industrial operations, such as are employed in the aerospace industry, thermocouples often are used to measure temperatures because of their relatively low cost and high reliability. Unfortunately, in order to provide for accurate measurements of temperature utilizing such devices, however, it is necessary to provide in combination therewith reference thermocouples maintained at constant temperatures throughout the duration of the temperature measuring operation in which the devices are employed.
Numerous devices have been proposed for use in heating reference thermocouples and many have been employed for this purpose. For example, see U.S. Pat. Nos. 2,559,571; 3,069,909; 3,345,540; and 3,648,523 which generally typify devices utilized in simultaneously heating the junctions of a multiplicity of reference thermocouples, herein referred to as a mulitple junction reference oven, or simply oven.
Heretofore, it has been common practice to provide in a multiple junction reference oven individual reference junctions displaced at uneven distances from a common source of heat. Alternatively, multiple heating elements are sometimes employed in heating the junctions. Such arrangements, of course, inherently result in temperature gradients being established between the various reference thermocouples with an attendent necessity that the gradients be, in some manner, taken into account or accommodated. Often, such requires the use of ovens of increased weight, size and complexity.
Moreover, in certain applications, such as in airborne data acquisition systems used in conducting flight tests, a relatively large number of temperature sensing thermocouples are required. Because of the inherent bulk and weight of the ovens of the prior art, as well as power requirements, limitations frequently are imposed on the number of reference junctions which can be accommodated, with an attendant reduction in the number of temperature sensing thermocouples which can be made available for a given test flight or similar operation.
It should therefore be apparent that there currently exists a need for a small, economic, and lightweight oven having capabilities for accommodating large numbers of thermocouple junctions, without temperature gradients being established between the various junctions employed to provide standard signals to which signals derived from temperature sensing thermocouples are compared.
It is therefore the general purpose of the instant invention to provide an improved oven for use in maintaining the junctions of reference thermocouples at constant temperatures in combination with a temperature sensing sytem characterized by a multiplicity of remotely related temperature sensing thermocouples.